Also known as the triad syndrome, Eagle-Barrett syndrome and the urethral obstruction malformation sequence, Prune-belly syndrome (PBS) is characterized by varying degrees of abdominal musculature hypoplasia, urinary tract anomalies and bilateral cryptorchidism. The incidence is approximately 1:40,000 live births, with over 95% of cases reported in males. PBS is associated with trisomy 18 and 21. The cause remains unknown, but two major theories predominate. The mesenchymal defect theory suggests early injury to the lateral plate mesoderm, from which the abdominal wall and genitourinary tract arise. The urethral obstruction theory suggests distal urethral obstruction in early gestation causes massive dilation of the bladder and ureters, forming a physical barrier to abdominal wall musculature development, prostate development and testicular descent.

Urinary tract abnormalities include varying degrees of megacystis and hydroureteronephrosis associated with absence of smooth muscle and functional obstruction of the urethra (lack of striated muscle in the membranous urethra and associated prostatic hypoplasia resulting in abnormal angulation), posterior urethral valves, urethral atresia and megalourethra. These anomalies predispose to impaired voiding, vesicoureteral reflux and stasis, urinary tract infections, pyelonephritis and renal hypoperfusion injury. The major prognostic factor is related to the degree of renal impairment. Patients with severe renal dysplasia and resultant pulmonary hypoplasia often die in the perinatal period. Those that survive, 30% will develop chronic renal insufficiency or end stage renal disease in childhood or adolescence. Patients with the mildest urinary tract involvement without obstruction have a normal life expectancy. Overall mortality rate in PBS is 60%.

Diagnosis is made prenatally or by visualization of the abdominal wall defect at birth. Initial assessment is aimed at identifying potentially life-threatening associations. Pulmonary hypoplasia results from oligohydramnios and is compounded by thoracic cage skeletal anomalies, abdominal muscle weakness and uremia. Cardiac anomalies are present in up to 10% and include patent ductus, atrial septal defect, ventricular septal defect and tetralogy of Fallot. Gastrointestinal malformations include intestinal malrotation, anal atresia, small bowel stenosis and volvulus in over 30% of patients. Non–life threatening associations include clubfoot, congenital hip dislocation, absence of limbs and digits, pectus excavatum, scoliosis, chronic constipation, developmental delays and growth retardation.